JPH068657A - Thermal transfer sheet - Google Patents

Abstract

PURPOSE:To improve recording sensitivity at the time of thermal printing and the sharpness of a printing image, in a thermal transfer sheet wherein an ink layer based on a colorant and a hot-melt compd. is arranged on a support, by providing a surface layer composed of hollow particles on the ink layer. CONSTITUTION:A thermal transfer sheet is constituted by arranging an ink layer based on a colorant and a hot-melt compd. on the upper surface of a support. In this case, a surface layer composed of hollow particles is provided on the upper surface of the ink layer and formed from hollow particles and wax particles. In this surface layer consisting of hollow particles and wax particles, the wax particles are formed from particles based on carnauba wax and a thermoplastic resin with an m.p. or softening point of 60-130 deg.C. By this constitution, the thermal transfer sheet good in recording sensitivity at the time of thermal printing and excellent in the sharpness of a printing image, the printability to a low smoothness receiving material and the friction resistance of a recording image is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer sheet, and more specifically, it has excellent recording sensitivity and has a sharpness of a printed image,
The present invention relates to a thermal transfer sheet having excellent printability on a low-smoothness receptor and excellent abrasion resistance of recorded images.

[0002]

2. Description of the Related Art Many proposals have been made to improve the recording sensitivity of a thermal transfer sheet. For example,
A low melting point substance is used for the transfer layer, and the transfer layer is melt-transferred with low energy. In order to effectively transfer the heat energy from the heating element to the transfer layer, a substance with good thermal conductivity is contained in or on the substrate surface. The method of making it proposed is proposed. In addition, an ink sheet using a heat-foamable material in the ink layer or in the surface layer in order to improve the recording property on the receptor having low smoothness (JP-A-59-201893, 60-8).
No. 2392, No. 60-236792, No. 62-144.
No. 992, etc.), an ink sheet in which a heat-melting material (wax, resin, etc.) or a pigment is added to the surface layer on the ink layer (JP-A-60-189489, 61-66694).
No. 62-21591, etc.), an ink sheet having a reticulated porous layer provided on the ink layer (JP-A-61-295).
No. 080) has been proposed.

[0003]

However, for example, in the above method, although the recording sensitivity is improved, a low melting point substance is used in the ink layer, so that the sharpness of the printed image is poor and the abrasion resistance is poor. Although there is a drawback and the other method improves the thermal conductivity of the substrate, it is difficult to obtain a sharp printed image because of large heat diffusion. Further, the ink sheet of (1) requires an extra amount of heat for foaming the heat-foamable material, which requires a larger amount of heat than that of a normal ink sheet, and it is difficult to improve the recording sensitivity.

In the ink sheet of No. 3, since the heat-fusible substance layer is simply provided on the ink sheet, the amount of the heat-fusible substance in the ink sheet increases, so that a larger amount of heat is required at the time of thermal transfer, No improvement in recording sensitivity can be expected. Moreover, since the surface layer of the ink sheet is a reticulated porous layer, the surface layer is not a complete discontinuous layer but a partial continuous layer, and therefore the surface layer is sheared during thermal transfer. The strength becomes large, it is difficult to obtain a sharp printed image, and the recording sensitivity is insufficient. In addition, a method has been proposed in which hollow particles are contained in the heat-soluble ink layer to enhance the cushioning property of the ink layer, but such a method makes it difficult for the ink layer to be sufficiently melted by heat, No improvement in thermal sensitivity can be expected.

The present invention has been made in view of the above circumstances, and is excellent in recording sensitivity during thermal printing, and is excellent in sharpness of a printed image, printability on a low-smooth receptor, friction of a recorded image, and the like. It is intended to provide a thermal transfer sheet.

[0006]

As a result of intensive studies, the present inventors have found that a thermal transfer sheet having a surface layer composed of hollow particles on an ink layer is suitable for the above purpose. Has been completed.

That is, according to the present invention, in a thermal transfer sheet in which an ink layer containing a colorant and a heat-fusible compound as a main component is provided on a support, a surface layer made of hollow particles is provided on the ink layer. A thermal transfer sheet characterized by the above is provided.

In the thermal transfer sheet of the present invention, since the surface layer composed of hollow particles provided on the heat-meltable ink layer has a high heat insulating effect, the heat applied to the ink sheet from the thermal head diffuses to the receptor side. It can be effectively used by heat-melting the heat-meltable substance on the ink sheet. Therefore, according to the thermal transfer sheet of the present invention, it is possible to heat-melt the ink layer with a smaller amount of heat than that of the conventional ink sheet, and as a result, high sensitivity recording can be achieved.

The present invention will be described in more detail below. As described above, the thermal transfer sheet of the present invention is characterized in that the surface layer made of hollow particles is provided on the ink layer. With this configuration, the thermal transfer sheet of the present invention can heat-melt the ink layer with a small amount of heat as described above,
It has excellent recording sensitivity. Further, since the surface layer is made of the particulate matter, the shearing force of the surface layer itself is low, and therefore the sharpness of the printed image becomes excellent.

The hollow particles in the ink layer are resin particles having a particle diameter of about 0.1 to 2.0 μm, and the inner hollow diameter has an inner pore diameter / particle diameter ratio of about 0.1 to 0.8. Those are preferable. The hollow particles are composed mainly of styrene, an acrylic / styrene copolymer, a vinylidene chloride / acrylonitrile copolymer and the like. In addition, it is possible to use hollow particles containing water, propane, n-butane, isobutane, or the like, or only a gas in the hollow interior.

Further, in the present invention, it is very preferable that the surface layer is formed of the hollow particles and the wax particles (claim 2). By using both of the above particles in combination, the adhesive force of waxes to the receptor, particularly the penetrating power to the low-smoothness receptor, is effectively reduced, and the image portion that tends to occur during recording on the low-smoothness receptor. It is possible to obtain a recorded image with less white voids.

In this case, examples of the waxes include natural waxes such as carnauba wax, candelilla wax, beeswax, wood wax, montan wax, spermaceti wax, and paraffin wax, microcrystalline wax, oxidized wax, polyethylene wax and the like. Wax; Other higher fatty acids such as margaric acid, lauric acid, mistyric acid, palmitic acid, stearic acid, frommenic acid, behenic acid and metal salts thereof; higher alcohols such as stearyl alcohol and behenyl alcohol; esters such as fatty acid esters of sorbitan And amides such as stearic acid amide and oleic acid amide.

The wax particles to be used in combination are preferably particles having a particle diameter of 0.1 to 4.0 μm obtained by emulsifying or dispersing the above waxes with a surfactant. When wax particles having a particle size of more than 4.0 μm are used, the degree of adhesion with the receptor is reduced, so the degree of adhesion of the printed image to the receptor is reduced, and voids and the like occur, resulting in good recording. You may not be able to get an image.

Further, in the present invention, it is particularly preferable that the wax particles in the surface layer are composed mainly of carnauba wax and a thermoplastic resin having a melting point or a softening point of 60 to 130 ° C. (claim) Item 3). By forming the surface layer of the mixed wax particles and the hollow particles, the adhesive force of the recorded image to the receptor can be further strengthened, and the stability of the recorded image is increased. In particular, it is possible to obtain an image having excellent abrasion resistance in recording at high temperature.

In this case, the melting point or softening point is 60 to 130.
Thermoplastic resin at ℃ is mixed with carnauba wax,
It is optimal to use them in a solid solution state, and it is preferable to emulsify or disperse them and use them in the form of particles. Examples of the thermoplastic resin include acrylic resin, methacrylic resin, styrene resin, vinyl acetate resin, vinyl chloride resin, vinylidene chloride resin, petroleum resin, terpene resin, phenol resin, olefin resin, ethylene / vinyl acetate copolymer resin. , Polyester resin, polyacetal resin, polyamide resin, or copolymers thereof.

In the surface layer of the present invention, the content of hollow particles in the surface layer is preferably 40% by weight or more of the surface layer, and when the content is less than 40% by weight, sufficient thermal sensitivity can be expected. Absent. The amount of the surface layer deposited is preferably 0.1 to 3 g / m ² , and if it is out of this range,
Problems such as insufficient thermal sensitivity and occurrence of voids may occur. Further, in some cases, a known polymer resin can be used as a binder for the surface layer. As the polymer resin in this case, for example, polyamide-based, polyester-based,
Polyurethane, vinyl chloride, vinyl chloride, vinyl acetate, cellulose, rosin, petroleum, styrene, butyral,
In addition to terpene-based and phenol-based resins, ethylene /
Examples thereof include vinyl acetate copolymers and ethylene / acrylic resins.

Examples of the support used in the present invention include plastic films having relatively high heat resistance such as polyester, polycarbonate, triacetyl cellulose, nylon and polyimide, as well as glassine paper, condenser paper and metal foil. There is a thickness of about 2 to 15 μm,
It is preferably in the range of 3 to 10 μm.

The surface of the support which is in contact with the thermal head (the surface opposite to the surface on which the ink layer is present) is
If necessary, by providing a heat resistant protective layer made of silicone rubber, silicone resin, fluororesin, polyimide resin, epoxy resin, phenol resin, melamine resin, nitrocellulose, cellulose acetate propionate, etc. Can improve heat resistance,
Alternatively, it is also possible to use a support material which cannot be used conventionally.

The ink layer in the present invention comprises a conventionally known heat-fusible layer. Specifically, the ink layer mainly comprises colorants, waxes and resins, and the composition is hot-melted or dispersed. It is formed by applying it as a liquid on a support and drying it. The colorant is appropriately selected from conventionally known dyes and pigments. The waxes and resins are selected from the same materials as those used for the surface layer.

In the present invention, a release layer containing known waxes and resins as main components may be provided between the ink layer and the support, if desired. In this case, waxes and resins can be selected and used from the same materials as those used for the surface layer.

[0021]

EXAMPLES The present invention will now be described in more detail by way of examples, but the present invention is not limited thereto.
All% and parts shown below are based on weight.

Example 1 On a polyester film having a thickness of 4.5 μm, the following (A
After drying, the coating liquid of (Component) was applied with a wire bar so that the amount of adhesion was 2.5 g / m ² , and dried to form a thermal transfer ink layer. (Component A) Carnauba wax aqueous dispersion 70 parts (average particle size 0.3 μm: solid content 30%) Carbon black aqueous dispersion (solid content 20%) 25 parts Polyvinyl alcohol aqueous solution (solid content 5%) 5 parts

After forming the above-mentioned thermal transfer ink layer, a coating liquid of the following (component B) is further applied onto the thermal transfer ink layer, and the adhesion amount after drying is 0.5.
It was coated with a wire bar so as to be g / m ² and dried to form a surface layer. (Component B) After dispersion of hollow particles (manufactured by Rohm & Hass: 60 parts Low Bake op-62: solid content 25%) styrene / butadiene copolymer emulsion 0.6 parts (solid content 50%) water 39.4 parts

On the surface opposite to the ink layer, a 1% solution of silicone rubber in toluene was applied by a smoothing bar so that the amount adhering to the surface was 0.05 g / m ² , and the back layer was dried. Was formed to obtain a thermal transfer sheet of the present invention.

Example 2 On one side of a PET film having a thickness of 4.5 μm, a release layer coating solution of the following (C component) was applied by a wire bar so that the amount of adhesion was 1.5 g / m ² and dried. Then, a peeling layer was formed. (Component C) Powdered carnauba wax (100 mesh whole) 9 parts Ethylene / vinyl acetate copolymer 1 part Toluene 60 parts MEK 30 parts Dispersed in a ball mill for 10 hours to give an average particle diameter of 3.0 μm.

Next, the thermal transfer ink layer coating liquid (component (A)) was applied onto the release layer so that the amount of adhesion after drying was 2.0 g / m ^2.
And a surface layer [using the (B component)] and a back layer were formed in the same manner as in Example 1 to obtain a thermal transfer sheet of the present invention.

Example 3 Example 2 was formed on a 4.5 μm thick polyester film.
After forming a peeling layer and a heat transferable ink layer in the same manner as above, a coating liquid of the following (D component) is further applied thereon by a wire bar so that the dry adhesion amount becomes 0.7 g / m ² , and dried. Then, the surface layer was formed. (D component) Hollow particle dispersion liquid (manufactured by Rohm & Hass: 40 parts Low Bake op-91: solid content 25%) Candelilla wax aqueous dispersion liquid 32 parts (average particle size 0.3 μm: solid content 30%) Methyl methacrylate / Polyacrylic acid copolymer 1 part / Ammonium salt aqueous solution (solid content 40%) Water 27 parts

Then, in the same manner as in Example 1, a back layer was provided on the surface opposite to the ink layer to obtain a thermal transfer sheet of the present invention.

Example 4 Example 2 was placed on a 4.5 μm thick polyester film.
After forming a release layer and a heat transferable ink layer in the same manner as above, a coating liquid of the following (E component) is further dried thereon and then coated with a wire bar so that the adhesion amount becomes 0.7 g / m ² and dried. Then, the surface layer was formed. (Component E) Hollow particle dispersion (same as in Example 3) 40 parts Solid solution particle dispersion of carnauba wax and ethylene / vinyl acetate with softening point 90 ° C. 32 parts Copolymer (9: 1) (average particle size 1 0.8 μm: solid content 30%) Methyl methacrylate / polyacrylic acid copolymer 1 part / ammonium salt aqueous solution (solid content 40%) water 27 parts

Then, in the same manner as in Example 1, a back layer was provided on the surface opposite to the ink layer to obtain a thermal transfer sheet of the present invention.

Example 5 Example 2 was placed on a 4.5 μm thick polyester film.
After forming a peeling layer and a heat transferable ink layer in the same manner as above, a coating liquid of the following (F component) is further dried thereon, and then coated with a wire bar so that the adhesion amount becomes 1 g / m ² and dried. , A surface layer was provided. (F component) Hollow particle dispersion liquid (same as in Example 3) 40 parts Organic polymer fine powder dispersion liquid 20 parts (Mitsui Toatsu Co., Ltd .; SP-MM: solid content 50%) Styrene / butadiene copolymer emulsion 1 Part (solid content 50%) water 39 parts

Then, in the same manner as in Example 1, a back layer was provided on the surface opposite to the ink layer to obtain a thermal transfer sheet of the present invention.

Comparative Example 1 In Example 1, except that the surface layer was not provided.
A thermal transfer sheet for comparison was prepared in the same manner as in Example 1.

Comparative Example 2 Comparative Example 2 was carried out in the same manner as in Example 3 except that the surface layer coating liquid of the following (G component) was used instead of the surface layer coating liquid of the (D component). A thermal transfer sheet was created. (Component G) Organic polymer fine powder dispersion 40 parts (Mitsui Toatsu Co., Ltd .; SP-MM: solid content 50%) Styrene / butadiene copolymer emulsion 1 part (solid content 50%) Water 59 parts

Comparative Example 3 Comparative Example 3 was carried out in the same manner as in Example 3 except that the surface layer coating liquid of the following (H component) was used in place of the surface layer coating liquid of the (D component). A thermal transfer sheet was created. (Component H) Hollow particle dispersion (same as Example 3) 24 parts Candelilla wax aqueous dispersion (same as Example 3) 47 parts Methyl methacrylate / polyacrylic acid copolymer 1 part / ammonium salt aqueous solution (solid content 40% water 28 parts

Regarding the thermal transfer sheets obtained in the above Examples and Comparative Examples, using a thermal transfer simulator, on a cast coated paper and a lightweight coated paper having a Beck smoothness of 200 seconds, a bar code pattern and a solid pattern under the following conditions. Was printed and evaluated according to the following method. The results are shown in Table 1.

Printing conditions Printing speed 100 mm / sec, Thermal head used: Thin film part glaze 8 dots /
mm.

Evaluation Method Thermal Sensitivity: A bar code is printed on cast coated paper, the decoding rate is calculated by LASER CHECK 2811 (manufactured by Symbol Technologies), and the value is represented by the minimum applied energy at which the value is 90 or more. Void: Beck is printed on a light-weight coated paper with a smoothness of 200 seconds, and the evaluation is made based on the unevenness of the printed area. ◯: Good print area is formed, ×: Clear print area is noticeable in the print area. Image abrasion resistance: A bar code is printed on cast coated paper, the printed image is subjected to a load of 100 g / cm ² at 50 ° C., and the printed image is rubbed 100 times, and the image is distorted. ⊚: No image distortion, ∘: There is image distortion or the like, but it is legible, ×: Image is distorted and is unreadable. Ground stain: Evaluated by the stain on the non-printed part when printing on a lightweight coated paper with Beck smoothness of 200 seconds.

[0039]

[Table 1]

From the results shown in Table 1, it can be seen that the thermal transfer sheet of the present invention is excellent in thermal sensitivity and image sharpness, and is also excellent in printing quality on a receiving paper having low smoothness.

[0041]

The heat transfer sheet of claim 1 has a constitution in which a surface layer made of hollow particles is provided on a heat-fusible ink layer, so that it has excellent recording sensitivity and excellent sharpness of a printed image. .

Since the surface layer of the thermal transfer sheet according to the present invention is composed of hollow particles and wax particles, a recording image with excellent print quality on a low-smoothness receptor and less voids can be obtained. The effect of being able to obtain is added.

Since the wax particles in the surface layer are composed mainly of carnauba wax and a thermoplastic resin having a melting point or a softening point of 60 to 130 ° C. The stability of the recorded image is improved, and the effect that an image having excellent abrasion resistance can be obtained is added.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Mitsuru Maeda 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (3)

[Claims] 1. A thermal transfer sheet in which an ink layer containing a colorant and a heat-fusible compound as main components is provided on a support,
A thermal transfer sheet comprising a surface layer made of hollow particles provided on the ink layer. 2. The thermal transfer sheet according to claim 1, wherein the surface layer comprises hollow particles and wax particles. 3. A surface layer comprising the hollow particles and wax particles, wherein the wax particles are particles mainly composed of carnauba wax and a thermoplastic resin having a melting point or softening point of 60 to 130 ° C. The thermal transfer sheet according to claim 2, which is characterized in that.